Electromagnetic indicators



Feb. 20, 1962 w. SINCLAIR ELECTROMAGNETIC INDICATORS Filed Oct. 1, 1957 Audible Signal Unit Tb Fixed Contact Member Indicating Surface Of SOURCE Armature 32 2 3 e r u t O m r A Inventor A Ja W p zw Attorney United States h tent @fiice BfiZZfiliZ Patented Feb. 20, SE52 3,922,502 ELECTROMAGNETKC INDECATGRS Wiliiam Sinclair, Beeston, Nottingham, England, assignor to Ericsson Telephones Limited Filed Get. 1, 1357, Ser. No. 687,580 Claims priority, application Great Britain Dec. 29, B56 9 Claims. (Cl. 340366) The present invention relates to electromagnetic indicators and particularly to visual indicators for use in telephone switchboards or the like.

In some telephone systems a plurality of such indicators each connected to a telephone station is arranged in one or more rows on the face of a switchboard, and each indicator provides a visual indication or signal when a call is originated by the associated station. It is desirable that such an indicator should occupy the minimum area of the face of the switchboard commensurate with the provision of an adequate visual indication, in order that the said face of the switchboard may be used to the utmost advantage. It is also desirable that the indication given by such an indicator should enable a calling station to be readily identified, and be clearly visible from within a large area radiating from the indicator. Furthermore, it is also desirable that the power required to operate the indicator should be of a small order in order to minimize the current consumption of the switchboard and in consequence the power of the operating means.

Electromagnetic visual indicators are known in which a pivoted armature is retained by gravity, or by pressure derived from a resilient spring, in a position where it is concealed from view, and moves into view when a magnetic field is produced at the pole face of an associated electromagnet. In such indicators the magnetic field either causes the armature to move towards the pole face or repels it away from the pole face. With an indicator of the former kind considerably more power is required to overcome the initial inertia of the armature than is required to maintain it in an operated position, while an indicator of the latter kind requires more power to maintain the armature in an operated position than is required to move it from its unoperated position. In consequence the power required to operate such indicators is not used to the utmost advantage at all times.

It is one object of tie invention to provide an improved visual indicator in which the ratio of visual indication to space occupied on the face of a switchboard is high, and with which the said visual indication is visible from within a wide area radiating therefrom.

It is another object of the invention to provide a visual indicator which utilizes a. low consumption of power to the utmost advantage.

According to the invention there is provided an electromagnetic indicator wherein the gap between the ends of the outer limbs of an E-shaped electromagnet is bridged by a magnetic member, and two armatures spaced equidistantly from the inner limb of said electromagnet are arranged to conceal said magnetic member when unoperated. In operation, the two armatures turn on axes which extend between the said outer limbs parallel to and equidistant from the said magnetic member and expose a face of said member.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawing, wherein:

FIGURE 1 is a perspective view of an embodiment of an electromagnetic indicator of the present invention;

FIG. 2 is a perspective view of a portion of the indicator of FIG. 1, with the armatures 32 in their operative positions;

FIG. 3 is a perspective view of the same portion of the indicator of FIG. 1, with components removed to illus- 2 trate the mounting of the spring 23 and the configuration of the pole piece 33;

FIG. 4 is a perspective view of the same portion of the indicator of FIG. 1, with components removed to illustrate the configuration of each armature 32;

FIG. 5 is a perspective view of the same portion of the indicator of FIG. 1, with components removed to illustrate the configuration of the spring 23; and

FIG. 6 is a perspective view of a modification of a portion of the indicator of FIG. 1.

An iron core 1 is fastened to two rectangular end checks 2 and 3 of insulating material, and one end of the core 1 which projects through the face of end check 3 is formed into a rectangular pole piece 4. The other end of the core 1 which projects through the face of end cheek 2 is threaded, and is screwed into threaded holes in a rectangular iron plate 5 and a U-shaped iron yoke 6 with two flat rectangular limbs 11 and 12 to form an E-shaped magnet. The threaded end of the core 1 extends beyond the threaded hole in the yoke 6 and is fastened to a wiring tag mounting block 7 of insulating material by a threaded nut (not shown). Wound upon core 1 between end checks 2 and 3 is an energizing winding 8 to the ends of which are connected to wiring tags 9 and iii of mounting block 7. The two outer limbs 11 and 12 of the E-shaped magnet extend beyond the face of pole piece" 4, and the end of each limb 11 and 12 has a small portion cut away at each side to form a stepped part on which a transparent guard 13 is fitted. Bridging the ends of the outer limbs 11 and 12 is a rectangular pole piece 33 of arcuate cross section with two rectangular studs 34 each of which projects from the central portion of one end. Each such stud 34 is fitted into an associated rectangular slot 35 in the outer limbs 11 and 12. Outer limb 11 is fastened to end check 3 by means of two threaded screws 14 which pass through counter-sunk holes in an L-shaped bracket 15 and through concentric holes in an insulating block 15, a fixed contact member 17 and an insulating plate 18, and screw into blind and tapped holes 19 in end cheek 3. The holes in insulating block 16 are provided with suitable raised perimeters arranged to fit within the holes in fixed contact member 17 in order to insulate fixed contact member 17 from screws 14. Outer limb 12 is fastened to end check 3 by two similar screws (not shown) which pass through counter-sunk holes in a rectangular piate 2t), and through suitable holes in an L-shaped bracket 21, and screw into blind and tapped holes in end cheek 3.

The outer limb 12 has a rectangular portion removed in a position adjacent to the lower end of pole piece 4 to form a rectangular hole 22, and the lower end of a resilient spring member 23 rests against the exposed face of bracket 21, and is retained within the hole 22 by a screw 24 which passes through concentric holes in rectangular plate 25 and bracket 21 and screws into a tapped hole 25 in spring member 23. The end of spring member 23.

beyond the hole 25 is formed into a wiring tag 26 which is connected by an insulated conductor to an associated wiring tag 27 on mounting block 7. Fastened to the upper face of outer iimb 12 adjacent to the rectangular hole 22, and in corresponding positions on the lower face of outer limb 11 are two cylindrical brass pivots 30 on which two channel shaped magnetic armatures 32 are fitted. Each pivot 30 forms a sliding fit within an associated hole 31 in an end of an armature 32, and the armatures 32 are arranged to turn on the pivots 30 from positions where they conceal the face 29 of pole piece 33 to positions where the said face 2% is revealed.

The central portion of spring member 23 which is cruciform in shape is arranged with one face substantially parallel to the face of pole piece 4, and with its horizontal arms 39 parallel to the horizontal edges of the said face and extending equidistantly beyond the adjacent vertical edge thereof. "the two horizonta arms 35 each bear against the vertical inner edge 36 of an adjacent armature 32, "and retain the. armatures 32 in positions where their front vertical edges 37 abut each other so that the face 2% of pole piece 33 is concealed from view. The vertical portion of the L-shaped upper end of springmember 23 projects through concentric rectangular holes in outer limb 11' and insulating plate 18 to form a moving contact member .23 which cooperates with fixedcontact member 17.

When a source of direct current is applied to the energizing winding 8 by way of Wiring tags 9 and 10 the indicator operates in the following manner. The magnetic flux produced in the E-shaped magnet is such that rectangular pole piece 4 is of one polarity and the pole piece 7 33 is of a different polarity. The resultant magnetic field between the pole pieces 4 and 33 polarizes armatures 32 in such a manner that the front vertical edges 37 repel eachother; and the plane faces 38 are attracted to pole piece 4. Thus the armatures 3- are caused to turn on pivots 36 against the pressure exerted by spring member Z-Tauntilthe plane face 38 of each armature 32 comes to rest against a side of pole piece 4, and the face 29 of pole piece 33 is revealed. In so doing the horizontal arms 39 of spring member 23 are moved away from the face of pole piece 4 causing a contact face of moving contact member 28 to bear against a contact face of fixed contact member 17. 7 'When the source of direct current is disconnected the magnetic field collapses and the plane faces 38 of arma- .tures 32 are no longer attracted to pole piece 4. The a pressure applied to'the' armatures 32 by the horizontal arms 39 of spring member 23 causes the arma-tures 32 to turn on the pivots 5% to their unoperated positions so that their front vertical edges 37 meet together and conceal the face 29'o-f pole piece 33. In so doing the contact face of'moving contact member 28 is moved away from the contact face of fixed contact member 17 and contact between them is broken. Fixed contact member 17 is provided with a wiring tag it to enable an electrical conductor to be connected thereto. Thus by connecting wiring tags 49 and 27' by way of suitable conductors to audible signalling means a circuit may be completed to the said means and audible signal given when the indicator is operated.

It is a' feature of the invention that the indicator is arranged to give a visual indication which is clearly visible from within a Wide area radiating therefrom by utilizing at least part of the inner surface of the armatures 32 as an indicating surface to augment the indicating surface formed by the face 29 of pole piece 33. The inner surfaces of the armatures 32 and the face 290i pole piece 33 are treated by coating them with a suitable colored medium and the remaining surfaces of the indicator are treated by coating them with a black medium. Thus when the operating indicator is viewed from any position within a wide area in the front thereof, at least part of the colored inner surface of the varmatures is visible in addition to the coloredface 29 of pole piece 33.

Although in the described embodiment of the invention the armatures are retained in an unoperated position by a common resilient spring member 23, in other embodiments of the invention each armature may be retained by a separate resilient spring as shown in PEG. 6. For example a helical spring may be arranged to fit around a pivot 39 between the end of an armature 32 and the adjacent limb 11 or 12, and one end of the said helical spring fastened to the pivot and the other end fastened to the armature.

' As the magnetic field of the E-shaped electro-magnet is utilized to the utmost advantage to both repel and attract the armatures from unoperated to operated positions, the power required to energize the Winding may be of a small order. a

' I claim: I

1. in an electromagnetic device, in combination, a pair of magnetizable pole pieces spaced from each other; a pair of symmetrically arranged armatures each having a side portion adapted to cooperate magnetically with said pole pieces, and an edge portion; and support means supporting said armatures adjacent said pole pieces symmetrically with respect to the latter and movably between two positions in a first of which positions the side portions of said armatures are spaced at muimum distance from said pole pieces and the edge portions of the said armatures are adjacent each other, and in the second of which positions the side portions of the said armatures are adjacent the said pole pieces and the edge portions of the said 'armatures are spaced 9. maximum distance from each other, said pair of armatures being positioned by said support means in such a manner in relation to said pair of pole pieces and in relation to each other that when the said pole pieces are simultaneously magnetized with different polarities the said armatures are in the magnetic field produced by the said pole pieces and corre sponding portions of the said armatures are magnetized with polarities different from that of one of the said pole pieces but similar in each of the said armatures so that said one of the said pole pieces when it is magnetized attracts the said armatures at said corresponding side portions thereof to urge the said armatures from the first position to the second position thereof and the said armatures repel each other at the edge portions thereof also to urge the said armatures from said first position to said second position thereof whereby the said armatures move from the said first position to the said second position thereof by the attraction of said one of the said pole pieces and the mutual repulsion of the said armatures.

.2. In an electromagnetic device, in combination, a first magnetizable pole piece having a face which is to be covered and uncovered; a swond magnetizable pole piece spaced from said first pole piece; a pair of symmetrically arranged armatures each having a side portion adapted to cooperate magnetically with said pole pieces, and an edge portion; and support means supporting said arma tures adjacent said pole pieces symmetrically with respect to the latter and movably between two positions in a first of which positions the side portions of said armatures are spaced a maximum distance from'said pole pieces and the edge portions of the said armatures are adjacent each other so that the said armatures at least partly cover the face of said first pole piece, and in the second of which positions the side portions of the said armatures are adjacent the said pole pieces and the edge portions of the said armatur es are spaced a maximum distance from each other so that said face of the said first pole piece is uncovered, said pair of armatures being positioned by said support means in such a manner in relation to said pair of pole pieces and in relation to each other that when the said pole pieces are simultaneously magnetized wit difierent polarities the said armatures are in the magnetic field produced by the said pole pieces and corresponding portions of the said armatures are magnetized with polarities different from that of said second pole piece but similar in each of the said armatures so that the said second pole piece when it is magnetized attracts the said armatures at said corresponding side portions thereof to urge the said armatures from the first position to the second position thereof and the said armatures repel each other at the edge portions thereof also to urge the said armatures from said first position to said second position thereof whereby the said armatures move from the said first position to the said second position thereof by the attraction of the said second pole piece and the mutual first pole piece; a pair of symmetrically arranged armatures each having a side portion adapted to cooperate magnetically with said pole pieces, and an edge portion; and support means supporting said armatures adjacent said pole pieces symmetrically with respect to the latter and movably between two positions in a first of which positions the side portions of said armatures are spaced a maximum distance from said pole pieces and the edge portions of the said armatures are adjacent each other so that the said armatures cover the face of said first pole piece, and in the second of which positions the side portions of the said armatures are adjacent the said pole pieces and the edge portions of the said armatures are spaced a maximum distance from each other so that said face of the said first pole piece is uncovered, said pair of armatures being positioned by said support means in such a manner in relation to said pair of pole pieces and in relation to each other that when the said pole pieces are simultaneously magnetized with ditferent polarities the said armatures are in the magnetic field produced by the said pole pieces and corresponding portions of the said armatures are magnetized with polarities different from that of said second pole piece but similar in each of the said armatures so that the said second pole piece when it is magaetized attracts the said armatures at said corresponding side portions thereof to urge the said armatures from the first position to the second position thereof and the said armatures repel each other at the edge portions thereof also to urge the said armatures from said first position to said second position thereof whereby the said armatures move from the said first position to the said second position thereof by the attraction of the said second pole piece and the mutual repulsion of the said armatures.

4. In an electromagnetic device, in combination, a substantially E-shaped structure having a pair of outer parallel elongated limbs and a central elongated limb located between and extending parallel to said outer limbs, said outer limbs respectively having free end portions spaced from and located beyond a free end portion of said central limb; a first elongated magnetizable pole piece having a face which is to be covered and uncovered, said first pole piece extending between and carried'by the free end portions of said outer limbs; a second elongated magnetizable poie piece spaced from and parailel to said first pole piece, said second pole piece being fixed to and carried by the free end portion of said central limb in spaced reiation to said outer limbs; a pair of symmetrically arranged armatures each having a side portion adapted to cooperate magnetically with said pole pieces, and an edge portion; and support means supporting said armatures adjacent said pole pieces symmetrically with respect to the latter and movabiy between two positions in a first or": which positions the side portions of said armatnres are spaced a maximum distance from said pole pieces and the edge portions of the said armatures are adjacent each other so that the said armatures cover the face of said first pole piece, and in the second of which positions the side portions of the said armatures are adjacent the said pole pieces and the edge portions of the said armatures are spaced a maximum distance from each other so that said face of the said first pole piece is uncovered, said pair of armatures being positioned by said support means in such a manner in relation to said pair of pole pieces and in relation to each other that when the said pole pieces are simultaneously magnetized with different polarities the said armatures are in the magnetic field produced by the said pole pieces and corresponding portions of the said armatures are magnetized with polarities diiferent from that of said second pole piece but similar in each of the said armatures so that the said second pole piece when it is magnetized attracts the said armatures at said corresponding side portions thereof to urge the said armatures from the first position to the second position thereof and the said armatures repel each other at the edge portions thereof also to urge the said armatures from said first position to said second position thereof whereby the said armatures move from the said first position to the said second position thereof by the attraction of the said second pole piece and the mutual repulsion of the said armatures.

5. In an electromagnetic device, in combination, a substantially E-shaped structure having a pair of outer parallel elongated limbs and a central elongated limb located between and extending parallel to said outer limbs, said outer limbs respectively having free end portions spaced from and located beyond a free end portion of said central limb; a first elongated magnetizable pole piece having a face which is to be covered and uncovered, said first pole piece extending between and carried by the free end portions of said outer limbs; a second elongated magnetizable pole piece spaced from and parallel to said firstpole piece, said second pole piece being fixedto and carried by the free end portion of said central limb in spaced relation to said outer limbs; a pair of symmetrically arranged armatures each having a side portion adapted to cooperate magnetically with said pole pieces, and an edge portion; and support means supporting said armatures adjacent said pole pieces symmetrically with respect to the latter and movably between two positions in a first of which positions the side portions of said armatures are spaced a maximum distance from said pole pieces and the edge portions of the said armatures are adjacent each other so that the said armatures cover the face of said first pole piece, and in the second of which positions the side portions of the said armatures are adjacent the said pole pieces and the edge portions of the said armatures are spaced a maximum distance from each other so that said face of the said first pole piece is uncovered, said support means being formed by the free end portions of said outer limbs and supporting the said armatures for turning movement about a pair of axes respectively parallel to the said pole pieces, said pair of armatures being positioned by said support means in such a manner in relation to said pair of pole pieces and in relation to each other that when the said pole pieces are simultaneously magnetized with diiferent polarities the said armatures are in the magnetic field produced by the said pole pieces and corresponding portions of the said armatures are magnetized with polarities different from that of said second pole piece but similar in each of the said armatures so that the said second poie piece when it is magnetized attracts the said armatures at said corresponding side portions thereof to urge the said armatures from the first position to the second position thereof and the said armatures repel each other at the edge portions thereof also to urge the said annatures from said first position to said second position thereof whereby'the said armatures move from the said first position to the said second position thereof b the attraction of the said second pole piece and the mutual repulsion of the said armatures.

6. in an electromagnetic device, in combination, a first elongated magnetizable pole piece having a face which is to be covered and uncovered; a second elongated magnetizable pole piece spaced from and parallel to said first pole piece; a pair of symmetrically arranged arma tures each comprising a substantially! channel-shaped member having a side portion adapted to cooperate magnetically with said pole pieces, an edge portion, and an intermediate portion located between the side and edge portion thereof and adapted to cover a portion of the face of said first pole piece; and support means supporting said armatures adjacent said pole pieces symmetrically with respect to the latter and movably between two positions in a first of which positions the side portions of said armatures are spaced a maximum distance from said pole pieces and' the edge portions of the said arrnatures are adjacent each other so that the saidarmatures cover the face of said first pole piece, and in the second-of which positions the side portions of the said armatures are adjacent the said pole pieces and the edge portions of the said armatures are spaced a maximum distance from each other so that said face of the said first pole piece is uncovered, said pair of armatures being positioned by said support means in such a manner in relation to said pairof pole pieces and in relation to each other that when the said pole pieces are simultaneously magnetized with diiferent polarities the said armatures are in the magnetic field produced by the said pole pieces and corresponding portions of the said armatures are magnetized with polarities difierent from that of said second pole piece but similar in each of the said armatures so that the said second pole piece when it is magnetized attracts the said armatures at said corresponding side portions thereof to urge the said mmatures from the first position to the second position thereof and the said armatures repel each other at the edge portions thereof also to urge the said annatures from said first position to said second position thereof whereby the said armatures move from the said first position to the said second position thereof by the attraction of the said second pole piece and the mutual repulsion or" the said armatures.

7. In an electromagnetic device, in combination, a first elongated magnetizable pole piece having a face which is to be covered and uncovered; a second elongated mag netizable pole piece'spaced from and parallel to said first pole piece; a pair of symmetrically arranged armatures each having a side portion adapted to cooperate magnetically with said pole pieces, and an edge portion;

support means supporting said armatures adjacent said pole pieces symrnctricallywith respect to the latter and movably between two positions in a first of: which posit-ions the side portions of said armatures are spaced 'a maximum distance from said pole pieces and the edge portions of the said armatures are adjacent each other so that the said armatures cover the face of said first pole piece, and in the second of which positions the side portions of the said armatures are adjacent the said pole pieces and the edge portions of the said armatures are spaced a maximum distance from each other so that said face of the said first pole piece is uncovered, said pair of armatures being positioned by said support means in such a manner in relation to said pair of pole pieces and in relation to each other that when the said pole pieces I when it is magnetized attracts the said armatures at said corresponding side portions thereof to urge the said armatures from the first position to the second position thereof and the said armatures repel each other at the edge portions thereof also to urge the said armatures from said first position to said second position thereof whereby the said armatures move from the said first posithe said armatures are adjacent each other so that the said armatures cover the face of said first pole piece, and in the second of which positions the side portions of the said armatures are adjacent the said pole pieces and the edge portions of the said armatures are spaced a maximum distance from each other so that said face of the said first polepiece is uncovered, said pair of armatures being positioned by said support means in such a manner in relation to said pair of pole pieces and in relation to each other that when the said pole pieces are simultaneously magnetized with difierent polarities the said armatures are in the magnetic field produced by the said pole pieces and corresponding portions of the said armatures are magnetized with polarities difierent from that of said second pole piece but similarin each of the said armatur'es so that the said second pole piece when it is magnetized attracts the said armaturcs at said corresponding side portions thereof to urge the said armatures from the first position to the second position thereof and the said armatures repel each other at'the edge portions thereof also to urge the said armatures from said first position to said second position thereof whereby the said armaturcs move from the said first position to the said second position thereof by the attraction of the said second pole piece and the mutual repulsion of the said armatures; and a spring of substantially cruciform shape tpositioned common 'to said armatures and yieldably tion to the said second position thereof by the attraction of the said second pole piece and the mutual repulsion of the said armatures; and sprin means cooperating with said armaturcs for yieldably maintaining the latter in the said first position thereof.

8. In an electromagnetic device, in combination, a first elongated magnetizable pole piece having a face which is to be covered and uncovered; a second elongated magnetizable pole piece spaced from and parallel tosaid first pole piece; a pair of symmetrically arranged armatdres each having a side'portion adapted to cooperate mag-' ne'tically with said pole pieces, and an edge portion; support means supporting said armatures adjacent said pole pieces symmetrically with respect to the latter and movably between two positions in a first of which positions the side portions of said armatures are'spaced a maximum distance from said pole pieces and the edge portions of maintaining the latter in the said first position thereof.

9. In an electromagnetic device, in combination, a substantially E-shaped structure having a pair of outer parallel elongated limbs and a central elongated limb located between and extending parallel to said outer limbs, said outer limbs respectively having free end portions spaced from and located beyond a free end portion of said central limb; a first elongated magnetizabie pole piece having a face which is to be covered and uncovered, said'first pole piece extending between and carried by the free end portions of said outer limbs; a second elongated magnetizable pole piece spaced from and parallel to said first pole piece, said second pole piece being fixed to and carried by the free end portion of said central limb in spaced relation to said outer limbs; a pair of symmetrically arranged armatures each having a side portion adapted to cooperate magnetically with said pole pieces, and an edge portion; support means supporting said armaturcs adjacent said pole pieces symmetrically with respect to the latter and movably between two positions in a first of which positions the side portions of said armatures are spaced a maximum distance from said pole pieces and the edge portions of the said armatures are adjacent each other so that the said armatures cover the face of said first pole piece, and in the second of which positions the side portions of the said armatures are adjacent the said pole pieces and the edge portions of the said armatures are spaced a maximum distance from each other so that said face of the said first pole piece is uncovered, said pair of armatures being positioned by said support means in such a manner in relation to said pair of pole pieces and in relation to each other that when the said pole pieces are simultaneously magnetized with ditfcrcnt polarities the said armatures are in the magnetic field produced by the said pole pieces and corresponding portions of the said armatures are magnetized with polarities different from that of said second pole piece but similar in each of the said armatures so that the said second pole piece when it is magnetized attracts the said armatures at said corresponding spring means mounted on an outer limb of said E-shaped structure and cooperating with said armatures for yieldably maintaining the latter in the said first position thereof. v

References Cited in the file of this patent UNITED STATES PATENTS 1,339,900 Lewis May 11, 1920 10 Hatton Apr. 3, 1956 Skrobisch May 27, 1958 Houdek Dec. 30, 1958 FOREIGN PATENTS Great Britain Apr. 10, 1941 Germany July 5, 1956 

